A device that can enlarge a displayed font may be preferred by certain users, such as middle-aged and old users. Conventionally, the displayed font is enlarged by a method of setting a global scale, such as in an Android operating system installed on the device. In this method, the displayed font may be in linear enlargement within an interval of [0, +infinity).
Although this method can enlarge the displayed font, the displayed font might be blindly enlarged even beyond an extent that can be accepted by a user. In addition, the displayed font is in linear enlargement, which may not flexibly adapt to requirements by application developers.